Actually array_intersect finds the dublicate values, here is my approach which is 5 times faster than built-in function array_intersect().. Give a try..

<?php
function my_array_intersect($a,$b)
{
        for($i=0;$i<sizeof($a);$i++)
        {
                $m[]=$a[$i];
        }
        for($i=0;$i<sizeof($a);$i++)
        {
                $m[]=$b[$i];
        }
        sort($m);
        $get=array();
        for($i=0;$i<sizeof($m);$i++)
        {
                if($m[$i]==$m[$i+1])
                $get[]=$m[$i];
        }
        return $get;
}
?>

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